High Testosterone Increases Premenopausal Breast Cancer Risk
Posted Dec 22 2010 9:56am
It is clear that many breast cancers are hormonally driven, that is the breast cancer cells contain receptors for estrogen (E) and progesterone (P) and these hormones can stimulate the growth of these breast cancer cells. Numerous research studies, including the large Women's Health Initiative , have shown that E+P hormone therapy increases breast cancer risk in postmenopausal women. However, less is known about the impact that naturally produced hormones have on breast cancer risk in premenopausal women. While the results of research studies have been inconsistent, there is some evidence that as a woman's lifetime exposure to circulating ovarian hormones increases, so does her breast cancer risk.
To explore this potential link between naturally produced ovarian hormones and breast cancer risk in premenopausal women, researchers measured blood levels of estradiol and testosterone in 266 study subjects, 98 of whom were diagnosed with in situ or invasive breast cancer ( paper is free to download ). Blood levels of these hormones were than analyzed in respect to breast cancer risk. The breast cancer researchers reported
Compared to women with total testosterone levels below 20 ng/dL, premenopausal women with with total testosterone levels above 34 ng/dL had more than a 300% increase in breast cancer risk.
Premenopausal women in the group with the highest quarter of bioavailable (free or unbound) testosterone were more than 4 times as likely to develop breast cancer compared to women in the lowest quarter of free testosterone levels.
Neither total nor free estradiol levels were linked to premenopausal breast cancer risk overall.
Further analysis looking at stages of the menstrual cycle suggested that premenopausal women with the highest follicular phase levels of total estradiol had a 2-fold increase in breast cancer risk.
This is a fascinating study in that it included analysis of testosterone levels as well as estradiol levels. When we think of hormones and breast cancer risk, estrogen (estradiol) and progesterone are the hormones that first come to mind. This new study clearly indicates that elevated testosterone blood levels can increase a premenopausal woman's breast cancer risk dramatically. While many think of testosterone as a male hormone, it is also a critical part of estradiol production in women. The lack of an overall effect of blood estradiol levels on premenopausal breast cancer risk was somewhat surprising; however, this was a small study and the investigators pointed out that the associations between estradiol levels and premenopausal breast cancer risk were erratic, which was likely due to the small number of study subjects and the normal fluctuation in estradiol levels across the menstrual cycle. While the relationship between premenopausal estradiol levels and breast cancer risk need further clarification, this study reports a dramatic increase in breast cancer risk with elevated blood testosterone levels. Measurement of blood testosterone levels might provide an opportunity to more clearly determine a premenopausal woman's breast cancer risk.